For example, as a container for storing ice cream, a storage container configured to seal the container by adhering a paper lid to a flange portion of a container body has been known (see, for example, Patent Literatures 1 and 2). From this storage container, the contents such as ice cream can be taken out by opening the center portion of the paper lid, which is not adhered to the flange portion. The paper lid described in Patent Literature 1 is provided with a tab for starting to open the storage container at a corner. The paper lid of the storage container is opened from the corner along the peripheral edge of the flange portion by separating the paper lid into the adhered portion and the center portion (lid portion) by delamination in the longitudinal direction and the lateral direction. Opening of the paper lid is realized by providing the lid with a back half-cut line formed by making half-cuts from the back side of the lid and a front half-cut line formed by making half-cuts from the front side of the lid to surround the back half-cut line, the back half-cut line and the front half-cut line being provided along the inner periphery of the flange portion, and by causing delamination of the paper substrate between these half-cut lines.